Ultra-light foam keeps indoor temperature 10 degrees cooler

In the report published in the journal Nano Letters On May 5, researchers designed an ultra-lightweight foam made of cellulose nanocrystals derived from wood that can reflect sunlight, emit absorbed heat, and insulate. According to them, this material can reduce more than a third of the energy required to cool the building.

Although scientists have developed many cooling materials, they still have many disadvantages. Some materials release a lot of heat absorbed through the building in direct midday Sun during the summer months. Other materials are not effective in hot, humid or cloudy weather. So, the team from Nanning Forestry University, aimed to develop a material that can reflect sunlight, release passive heat and prevent heat from passing through the building.

To produce the cooling material, the researchers bonded cellulose nanocrystals together with a bridge made of a silane compound before freezing and sublimating the material in a vacuum chamber. This process causes the nanocrystals to align vertically, creating an ultralight foam that reflects 96% of visible light and emits 92% of the absorbed infrared radiation.

When coated on top of a foil-lined box placed outdoors at noon, the material helps to keep the temperature inside the box 9.2 degrees Celsius lower than the outside temperature. Moreover, the material also maintains a temperature inside the box which is 7.4 degrees Celsius cooler than outside in wet conditions. When foam made from cellulose has been tightly pressed, its cooling capacity is reduced, revealing a variety of adjustable properties.

The team calculated that if cooling foam was placed on the roof and outside walls of a building, the energy demand for cooling would be reduced by an average of 36.4%. The performance of wood-based cellulose foam can be adjusted according to weather conditions. The technology can be applied in a variety of environments, the researchers say.

An Khang (According to Phys.org)